read data from serial port

mrjj

hi
In not sure why split and toInt dont work for u ?

QString input{"85,2018/8/3,17:21:3"};
QStringList values = input.split(",");
qDebug() << values[0].toInt();

gives 85.

isan

@mrjj I read from serial in while
and get 314 sps per second ,
and push_back them in string ,when I use the split it do it from the beginning of string NewValue , it doesn't split just new line that receive
and .toInt() return zero
how can do it just for new line data that receive?

mrjj

@isan
You mean data comes like
85,2018/8/3,17:21:3
85,2018/8/3,17:21:3
85,2018/8/3,17:21:3
85,2018/8/3,17:21:3
with newline in between ?

isan

@mrjj the data that receive is like:
when print with qDebug<<NewValue.c_str();
85,2018/8/3,17:21:3
98,2018/8/3,17:21:3
102,2018/8/3,17:21:3
9,2018/8/3,17:21:3
.......(until 314 samples )
167,2018/8/3,17:21:4
34,2018/8/3,17:21:4
28,2018/8/3,17:21:4
85,2018/8/3,17:21:4
.......(until 314 samples )

mrjj

so every time value variable is \n
you have a full line in NewValue and can split and take value.

isan

@mrjj with this:

QStringList values = input.split(",");
qDebug() << values[0].toInt();

that you said?
I change my code:

void MyThread::run()
{

    qDebug("Thread id inside run %d",(int)QThread::currentThreadId());

    int fd ,x;
    
      
    if ((fd = serialOpen ("/dev/ttyACM0",230400)) < 0)
    {
        fprintf (stderr, "Unable to open serial device: %s\n", strerror (errno)) ;
    }

    while (serialDataAvail(fd)>-2)
    {
         //-------value format is int-------
        value=serialGetchar (fd) ;
    //--------vs format is QString------
    vs.push_back(value);
     //--------values format is QStringList------
     values = input.split(",");
      x= values[0].toInt();
 msleep(1); 
       emit signalValueUpdated(x);
  
    }
    serialClose(fd); 
}

the first line that receive is 96,2018/8/3,21:35:40
the emit signalValueUpdated(x); is 96 for ever

mrjj

hi
well you only ask for first value!
values = input.split(","); // makes long list (potentially )
x= values[0].toInt(); // take only first in list

so it would be more like

for ( const QString& valline : values ) {
      qDebug() << "val =" << valline.toInt();
    }

and since list also contains other data, it looks like
96
2018/8/3
21:35:40
80
2018/8/3
21:35:40
90
2018/8/3
21:35:40
so value every 3 index

isan

@mrjj I should use this :

for ( const QString& valline : values ) {
    qDebug() << "val =" << valline.toInt();
  }

instead of this :

x= values[0].toInt();

am I right?

qDebug() << "val =" << valline.toInt();

always returns zero to me!

mrjj

@isan
hmm
maybe input is not as you expect then.
try qDebug() << values;
to see what it has

isan

@mrjj said in read data from serial port:

qDebug() << values;

return :
\n191", "2018/8/3", "23:28:55 \r\n187", "2018/8/3", "23:28:55 \r\n185", "2018/8/3", "23:28:55 \r\n164", "2018/8/3", "23:28:55 \r\n131", "2018/8/3", "23:28:55 \r\n103", "2018/8/3", "23:28:55 \r\n....................................

mrjj

Ok so when we only split at ","
We get \n\r on some/all of the values.
Using something Like ReadLine might be easier.
but you seem to use native serial comm and not Qt version?
but you can try
for ( const QString& valline : values ) {
qDebug() << "val =" << valline.trimmed().toInt();
}
Trimmed() should remove the \n\r
http://doc.qt.io/qt-5/qstring.html#trimmed

ah. wait.
it looks like some of the values are in same index as timestamp
"23:28:55 \r\n187"

mrjj

Hi
Im not really sure what is happening.
Seems to not to be structured as we think/needs more splitting

QString input{"85,2018/8/3,17:21:3\\n\\r85,2018/8/3,17:21:3\\n\\r95,2018/8/3,17:21:3"};
  QStringList lines = input.split("\\n\\r");
  for ( const QString& line : lines) {
    QStringList values = line.split(",");
    for ( const QString& valline : values ) {
      qDebug() << "val =" << valline.trimmed().toInt();
    }
  }

val = 85
val = 0
val = 0
val = 85
val = 0
val = 0
val = 95
val = 0
val = 0

when do you start processing the input ?
After it all have been read or how do u know that input is ready ?

isan

@mrjj it's return zero and sometimes 2018

when do you start processing the input ?
After it all have been read or how do u know that input is ready ?

I'm not sure what you mean?
read from serial port in thread and thread start in other class constructor.
so it's start when program run!
data send from arduino that connected to raspberry pi with USB port

mrjj

@isan
Looking at the code, it seems to me you
send al data and thread will read it all. and then close serial.
so

while (serialDataAvail(fd) > -2) {
  //-------value format is int-------
  value = serialGetchar (fd) ;
  //--------vs format is QString------
  vs.push_back(value);  
 }
 serialClose(fd);
 
 // here u should have complete data and can use 
to get the values if data is complete
input would be vs

  QStringList lines = input.split("\\n\\r");
  for ( const QString& line : lines) {
    QStringList values = line.split(",");
    for ( const QString& valline : values ) {
      qDebug() << "val =" << valline.trimmed().toInt();
    }
  }
}

JonB

@mrjj
I have no idea of the implications, but you have pasted code for OP as:

  QStringList lines = input.split("\\n\\r");

If he is supposed to be copying this, shouldn't he be using

  QStringList lines = input.split("\r\n");

Or, from his qDebug(), does it mean that the input literally has the 4-character sequence \r\n in it, and not CR-LF? In which case he would want

QStringList lines = input.split("\\r\\n");

mrjj

@JonB
Thank you , yes u are right its \r\n :) (of cause)
or \r\n when escaped.

JonB

Now, going back to where @isan wrote:

return :
 \n191", "2018/8/3", "23:28:55 \r\n187", "2018/8/3", "23:28:55 \r\n185", "2018/8/3", "23:28:55 \r\n164", "2018/8/3", "23:28:55 \r\n131", "2018/8/3", "23:28:55 \r\n103", "2018/8/3", "23:28:55 \r\n....................................

So if that's really right, after first splitting on "\r\n" (not even certain about that if the input really starts as shown with just \n and not \r\n, I'll just assume it's really \r\n), he then needs to split on "\",\"", not just plain ,. Then at the end of that you have 3 clean tokens per line.

I have to say the input looks a bit oddly tokenized/quoted, but that's what corresponds to the input he shows. If you're not careful and leave " characters in, you'll get toInt() returning 0 where you don't expect.

mrjj

@JonB
Hi
I think the "s comes from qDebug and is not in the input. (looking at the sending code higher up)
It seems he reads the entire load in one go and closes port so that means he should be able to
read complete string and then split it. ( i hope )

isan

@mrjj said in read data from serial port:

@isan
Looking at the code, it seems to me you
send al data and thread will read it all. and then close serial.
so

while (serialDataAvail(fd) > -2) {
  //-------value format is int-------
  value = serialGetchar (fd) ;
  //--------vs format is QString------
  vs.push_back(value);  
 }
 serialClose(fd);
 
 // here u should have complete data and can use 
to get the values if data is complete
input would be vs

  QStringList lines = input.split("\\n\\r");
  for ( const QString& line : lines) {
    QStringList values = line.split(",");
    for ( const QString& valline : values ) {
      qDebug() << "val =" << valline.trimmed().toInt();
    }
  }
}

Data is always sent and It does not go out of while() and I can not wait for complete data
Upon receive, I must use the data in other classes
I should not miss any data, if I close the port, the data will be lost

mrjj

@isan
ok so it must be on the fly.

Then you need to use 2 buffers as not to parse already received data over and over.
so in pseudo code

Read char from serial
tempbuffer += char
if char is \n then
split tempbuffer
emit value
clear tempbuffer

//i assume u want to store all ?
Mainbuffer +=char